1. Field of the Invention
The present invention relates to a substrate processing apparatus that applies processing using a processing liquid to various kinds of substrates represented by a semiconductor wafer, a glass substrate for liquid crystal display, a glass substrate for plasma display, a glass substrate for FED (Field Emission Display), an optical disc substrate, a magnetic disc substrate, a magneto optical disc substrate, a photomask substrate, and so forth.
2. Description of Related Art
In the fabrication sequence of a semiconductor device and a liquid crystal display, processing to clean the surface of a substrate, such as a semiconductor wafer and a glass substrate for liquid crystal display panel, using a processing liquid is performed by supplying the processing liquid to the surface of the substrate.
For example, an apparatus of a single substrate processing type that applies cleaning processing to substrates one by one includes a spin chuck that rotates a substrate while holding the substrate almost in a horizontal posture and a nozzle that supplies a processing liquid to the surface of the substrate being rotated by the spin chuck. During the processing, a processing liquid is supplied from the nozzle to the surface of the substrate at near the center of rotation while the substrate is rotated by the spin chuck. The processing liquid supplied onto the surface of the substrate experiences a centrifugal force induced by rotation of the substrate and flows over the surface of the substrate toward the outer edge thereof. The processing liquid is thus distributed across the entire surface of the substrate and rinse processing for the surface of the substrate using the processing liquid is achieved.
As a typical spin chuck, a spin chuck of a vacuum contact type that holds the substrate by means of vacuum contact to the bottom surface (the surface faced down) of the substrate and a spin chuck of an edge face pinching type that holds the substrate by pinching the edge face of the substrate with plural chuck pins are known. However, the spin chucks of both the vacuum contact type and the edge face pinching type cannot help coming into contact with the substrate, and a trace of contact may possibly be left on the substrate.
As a result, attention is recently attracted to a spin chuck of a non-contact type that has a substrate-opposing surface disposed oppositely to the bottom surface of the substrate with a microscopic distance, and supports the substrate by exploiting the Bernoulli effect produced by supplying a nitrogen gas from the substrate-opposing surface to a space between the substrate-opposing surface and the bottom surface of the substrate. Because the spin chuck of the non-contact type is able to support the substrate without coming into contact with the substrate, there is no risk of leaving a trace of contact on the substrate.
When the spin chuck of the non-contact type is adopted, however, the surface of the substrate subject to processing is limited to the top surface (the surface faced up). More specifically, it is only possible to process the top surface of the substrate by supplying the processing liquid to the top surface of the substrate, and because the processing liquid cannot be supplied to the bottom surface of the substrate at the same time, it is impossible to process both the top surface and the bottom surface of the substrate concurrently. Hence, when the both surfaces need to be processed, after one surface of the substrate is processed, the substrate has to be inverted vertically to apply the processing to the other surface. This extends a time needed to process a single substrate.